The basal ganglia play a crucial role in the neural control of voluntary movement. Diseases of the basal ganglia include Parkinsonism, Huntington's Chorea, Sydenham's Chorea, atheosis and hemiballismus. The present proposal is aimed at continuing an ongoing research program employing the comparative approach to a study of the role of the basal ganglia in the neural control of behavior. Studies of the basal ganglionic system in avian and reptilian forms indicates that th paleostriatum in these species exerts a major influence over the functioning of the opiatic tectum. This suggests that a phylogenetically ancient function of the basal ganglia concerns the modulation of attentional and orientation processes. Other results indicate that the specific organization of the avian and reptilian forebrain allows an analysis to be carried out on the information procesing characteristics of the basal ganglia in these species which would be extremely difficult or event impossible in mammalian forms. Specific experiments concern the continued study of the cytology and anatomy of the basal gnaglia. The possible role of the basal ganglia in controlling the position of the organism in space and in regulating the organism's body posture is also discussed in this proposal.